It is well known, in general, to provide skateboard-type structures with means for gliding on ice. For example, U.S. Pat. No. 4,043,565 describes a recreational device having an elongated board-like member for supporting the user and runner mounting means affixed in tandem to the underside of the member. Two pairs of parallel ice runners are in turn attached to the runner mounting means. Each runner has a plurality of ice contacting portions selectively positionable for contact with the ice. Suggested shapes for the runners include convexually arcuate polygon runners, circular runners, and oval shaped runners. The runners are designed in such a fashion to allow portions of the runner which have become dull to be repositioned by loosening and retightening a nut to hold an additional selected portion of a blade in contact with the ice. This allows the blade to be repositioned at any time to bring selectively different portions of the runner into contact with the ice as desired by the user.
U.S. Pat. No. 4,114,913 describes a skateboard having front and rear pairs of narrow runners or blades that enable a skateboard to be used on ice. To permit lateral movement, the edges on one pair of blades must be sharper than the edges on the other pair of blades. The blade edges are concave or angular. In all cases, the blade edges are symmetrical in cross-section. Each runner or blade is attached to a threaded stud which is in turn attached to a truck secured to the bottom of the skateboard platform.
U.S. Pat. No. 4,225,145 describes a modified skateboard having runners joined to existing trucks for use on snow or ice. Top and bottom rails of the runners are jointed and slotted to allow changing runner length upon turning. Right and left turns are achieved by shifting the weight from side to side and sliding the runners relative to the trucks. Elongated runners are curved upward at the front of the skateboard for easy turning and may be curved downward at the rear of the skateboard to provide greater stability for either straight-running or turning. The runners are symmetrical in cross-section, and are concave or have angular edges.
U.S. Pat. No. 4,521,029 discloses a skateboard adapted for use on ice which includes two pairs of skates with concave edges mounted for pivotal movement about axles which extend laterally from trucks mounted to the skateboard platform. Each skate includes an upwardly-extended protrusion which is covered by a bumper guard of resilient material for engaging the underside of the board, thereby limiting the pivotal movement of the runners and preventing the board from pitching forward and engaging the ice.
U.S. Pat. No. 4,896,893 describes a skateboard for use on ice having a pair of runner blades attached to horizontal axles which are associated with front and rear trucks attached to the skateboard platform. The runner blades either extend from axle to axle or, alternatively, auxiliary blades are attached to each side of the skateboard between the front and rear trucks and in tandem with the attached runner blades to the axles. The auxiliary blades are fixed in place and provide both added stability and the ability to turn while more weight is being exerted on one side of the deck of the skateboard. Normally the auxiliary blades are elevated and touch the ground one at a time and only as a result of weight being exerted from one side of the deck.
In view of the foregoing, it is readily apparent that the prior art devices have various drawbacks which are undesirable. For example, all of the prior art devices have blades or runners which are made almost in their entirety of steel or similar metal. Such blades or runners are constructed from metals to prevent rapid dulling and to allow resharpening of these materials with use. Moreover, the prior art blades are substantially unsupported in the lateral direction and must, therefore, be thickened to overcome this lack of support. Moreover, the positions of the blades or runners found in the prior art are fixed or otherwise restricted in their rotation or in their positioning, thereby preventing free rotation. Thus, each time the blades become dull, they must be either resharpened or, if possible, the position of the blades manually adjusted to bring a sharper portion of the blade in contact with the ice. Finally, the blade edges on prior art devices are symmetrical in cross-section which, as discussed below, is deleterious to the maneuverability of the device.